1. Technical Field
The present invention relates in general to hard disk drives and, in particular, to an improved system, method, and apparatus for enhanced cooling of voice coil motors in hard disk drives.
2. Description of the Related Art
Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm). Hard disk drives have several different typical standard sizes or formats, including server, desktop, mobile (2.5 and 1.8 inches) and microdrive.
A typical HDD also uses an actuator assembly to move magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
A slider is typically formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.
The head and arm assembly is linearly or pivotally moved utilizing a magnet/coil structure that is often called a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting with its spindle, actuator VCM, and internal filtration system is then enclosed with a cover and seal assembly to ensure that no contaminants can enter and adversely affect the reliability of the slider flying over the disk. When current is fed to the motor, the VCM develops force or torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop and settle directly over the desired track.
During operation, the VCM is prone to heat up to maintain fast seek times in high performance server class disk drives. Accordingly, the temperature of the VCM must be monitored since excessive temperature can degrade performance of the drive. In some operating environments and severe cases, the high temperatures generated by disk drives can melt the coil insulation and coating, thus resulting in catastrophic failures in the drive, such as outgassing, contamination, etc.
Some disk drives utilize a bypass channel to regulate airflow within the disk drive. With bypass architecture, the airflow is stripped from the disk pack, commonly by a diverter or spoiler, and diverted into the bypass channel. Ideally, the bypass channel should have no interruptions or leakage in order to maintain the airflow momentum throughout the channel. Unfortunately, this poses a dilemma for temperature-sensitive areas of the drive, such as the VCM, since bypass channels allow little or no flow into the VCM area. Thus, an improved airflow solution that satisfies the multiple and sometimes conflicting interests of bypass architecture would be desirable.